$form['mimetype']['#description'] = $this->t('Mimetype to convert to (e.g. application/xml, etc...)');
$form['mimetype']['#value'] = 'text/plain';
$form['mimetype']['#type'] = 'textfield';
unset($form['args']);
$form['args']['#description'] = $this->t("Arguments to send to Tesseract. To generate hOCR, use:<br/><code>-c tessedit_create_hocr=1 -c hocr_font_info=0</code>");